Individuals with cervical level spinal cord injury (SCI) can achieve significant functional gains using an implanted upper extremity neuroprosthesis, including the ability to be more independent in activities of daily living, such as eating, personal hygiene and office tasks. We hypothesize that further significant increases in functional outcomes can be obtained by expanding the alternatives for control of implanted neuroprosthetics. We have recently discovered that most, if not all, individuals who have been classified as having a "motor complete" cervical level spinal cord injury actually retain some voluntary control over lower leg muscles. Subjects were not aware of their ability because the movements were not visible or palpable. One of the important practical implications of this research is that subjects who are considered complete may have voluntary control over one or more lower extremity muscles that could be utilized as myoelectric control sources for a neuroprosthetic system. We refer to these muscles as "below injury control sources" (BICS). This discovery opens up significant opportunities that will be pursued in this study. We propose to screen a cohort of 50 motor complete cervical level SCI subjects to identify the prevalence of BICS. We will develop training methods targeted at improving the control of the weak muscles identified through the screening process. We will train a subset of the screened subject to determine whether improved performance can be obtained with targeted training using visual and electrocutaneous feedback. At the conclusion of this study we will have evaluated the potential suitability of BICS for neuroprosthetic use and will be prepared to utilize BICS to improve neuroprosthetic function in a future proposal. PUBLIC HEALTH RELEVANCE: Cervical spinal cord injury can result complete paralysis, particularly loss of hand and arm function. Some function can be restored through the use of electrical stimulation of the paralyzed muscles. Individuals control these systems through activation of muscles above the level of injury. In this project, we are exploring the recent discovery that many paralyzed individuals have very weak control over many muscles below their injury that were previously considered completely paralyzed. Although these muscles are far too weak to provide movement on their own, they might be able to be used to control stimulated muscle function.